During recent decades, antenna technology has experienced an increase in the use of antennas that utilize an array of antenna elements, one example of which is a phased array antenna. Antennas of this type have many applications in commercial and defense markets, such as communications and radar systems. In many of these applications, broadband performance is desirable. Some of these antennas are designed so that they can be switched between two or more discrete frequency bands. Thus, at any given time, the antenna is operating in only one of these multiple bands. However, in order to achieve true broadband operation, the antenna needs to be capable of satisfactory operation in a single wide frequency band, without the need to switch between two or more discrete frequency bands.
One type of antenna element that has been found to work well in an array antenna is often referred to as a tapered slot antenna element. The spacing between antenna elements in an array antenna is typically determined by the frequency at which the antenna operates, and a tapered slot antenna element fits comfortably within the space available for an antenna element in many array antennas.
Existing tapered slob antenna elements typically have a bandwidth of about 3:1 to 4:1, although some have a bandwidth that approaches 6:1. While these existing tapered slot antenna elements have been generally adequate for their intended purposes, they have not been satisfactory in all respects. In this regard, there are applications in which it is desirable for a tapered slot antenna element to provide broadband performance involving a bandwidth in the neighborhood of 10:1, or even larger. Existing designs and design techniques have not been able to provide a tapered slot antenna element which approaches this desired level of broadband performance.